Research On Urban Expansion And Its Ecological Environment Response In The Context Of New Urbanization

Since the reform and opening up,China’s urbanization process has been accelerating,residents’ living standards have improved significantly,and the national comprehensive strength has been improved steadily.However,this "rapid" development model has also brought many problems,especially the socio-economic and ecological environmental problems caused by urban expansion,which are becoming more and more serious in China and even in rapidly developing countries or regions around the world,and the Manland contradiction is becoming increasingly prominent.Long-term rapid urbanization has led to the rapid expansion of construction land,and a large amount of ecological land around the city has been squeezed and occupied,which seriously threatens ecological security.At the same time,rapid and blind urban expansion has led to massive emissions of pollutants such as waste gas,waste water,and solid waste and excessive consumption of resources,thus putting enormous pressure on the ecological environment.Facing the conflicts between natural resource constraints,serious environmental pollution,ecosystem degradation,and regional socio-economic development,taking a new urbanization path in line with the green,low-carbon,economical and intensive,ecological civilization development model is the key to regional high-quality development in the new era.Therefore,this thesis constructs a theoretical analysis framework of urban expansion and ecological environment response from the connotation of new-type urbanization,combined with the guidance and requirements of new-type towns on urban expansion.Subsequently,a research method system based on the path of "pattern process-spatial and temporal response-coupling and coordination-mechanism of action" is established to conduct a comprehensive and systematic study on the characteristics of urban expansion,the evolution of the ecological environment,as well as the coordinated development and mechanism of urban expansion and ecological environment.Finally,taking the urban agglomeration in the middle reaches of the Yangtze River as an example to carry out empirical research.The main conclusions of this study are as follows:(1)Spatio-temporal evolution characteristic of urban expansionThis study clarifies the urban expansion at different stages using the expansion intensity index and expansion difference index,identifies urban expansion patterns with the help of the landscape pattern index,and uses exploratory spatial data analysis and geographical detector to reveal the spatial correlation characteristics and the influencing factors of urban expansion.The results of the empirical study show that the characteristics of urban expansion intensity index at the urban agglomeration and the city scale can be summarized as "rising-rising-declining","declining-rising-declining" and "risingdeclining-declining" in the time series.Overall urban expansion intensity shows a decreasing trend in the later period.The spatial distribution shows an unbalanced expansion pattern at different times with different expansion rates,and the cities with moderate to high expansion rates are mainly concentrated in Hubei.According to the results of the expansion pattern identification,both urban agglomeration scale and cityscale show an expansion pattern dominated by edge-expansion and supplemented by infilling and outlying.The three expansion patterns exhibit four variation characteristics in the time series,namely "outlying decline-edge-expansion decline-infilling rise,""outlying rise-edge-expansion decline-infilling rise," "outlying rise-edge-expansion rise-infilling decline," and "outlying rise-edge-expansion decline-infilling decline.The global Moran’s I indexes of urban expansion intensity in urban agglomeration is greater than 0,and there is a positive correlation in geographic space.The results of cold hotspot analysis show that the hotspot areas are mainly distributed in Wuhan,Changsha,and Nanchang and their neighboring urban areas.The results of the Geodetector show that urban expansion in urban agglomerations is more significantly driven by secondary and tertiary GDP.The explanatory power of each driving factor on urban expansion after the interaction is greater than that of the two factors alone.(2)Spatio-temporal patterns of the ecological environment responseBased on the pressure-state-response model,this study combines the direct and indirect responses of the ecological environment to urban expansion to construct a comprehensive evaluation index system of ecological environment response.The analytic hierarchy process and entropy weight method is used to determine the subjective and objective composite weights of each index.Finally,we use a multi-factor comprehensive evaluation method to measure the ecological environment quality index and classify the ecological environment quality level of each region according to the criteria.The results of the empirical study show that the remote sensing ecological index of the urban agglomeration shows an increasing trend,and the regional ecological quality condition has improved.The cities at the below-medium level are concentrated in Wuhan and its surrounding cities.The results of the comprehensive evaluation of the ecological environment response of urban agglomeration show that the ecological environment quality index has increased but the growth rate has gradually become smaller.At the city level,there are differences in the changes of ecological environment quality at different stages,but there is no dramatic change in general.The ecological environment quality in Xiangyang,Ezhou,Jingmen,Changsha,and Xinyu with stable and unchanged levels,and steadily increased in Pingxiang throughout the study period,and in Yichang decreased compared to the initial period.In terms of spatial distribution,areas with ecological environment level at 4-5 are mainly concentrated in Wuhan as the center and its surrounding cities.Areas with ecological environment level at 7-8 are concentrated in the contiguous area of Jiujiang,Shangrao,and Jingdezhen.While the Changsha-ZhuzhouXiangtan urban agglomeration has transformed from a medium level to a higher level.(3)Spatial-temporal differentiation of coordinated development between urban expansion and ecological environmentBased on the connotation and guiding requirements of urban expansion in the context of new urbanization,this study constructs a comprehensive evaluation system of urban expansion and explores the relationship between urban expansion and ecological environment with the help of coupled coordination model.The results of the empirical study show that the urban expansion index of urban agglomerations has experienced a shift from rapid growth to stable growth during the study period,and the gap between cities gradually decreased indicating an overall shift from unbalanced to balanced development.The urban expansion level of the provincial capital cities has significantly increased compared with other cities,with Wuhan consistently having the highest level of urban expansion within the urban agglomeration.The degree of coordinated development of urban agglomerations has improved,and the regions changed from mild imbalance to relative coordination.Since 2015,several cities in Hubei have reached the coordinated development of urban expansion and ecological environment,among which Wuhan has been in a state of ecological environment lagged behind urban expansion after2010.(4)The mechanism of urban expansion on the ecological environmentThis study analyzes the degree of association between various factors of urban expansion and ecological environment based on the gray correlation analysis model to initially sort the influencing factors of urban expansion on the ecological environment.At the same time,factor dimensionality reduction is achieved based on covariance and correlation,and dominant factors are identified.Finally,the ordinary least squares(OLS)model is introduced to explore the mechanism of urban expansion on the ecological environment.The results of the empirical study show that the dominant factors influencing the spatio-temporal evolution of the ecological environment in the middle reaches of Yangtze River urban agglomeration are population density,average land value of secondary and tertiary output,land use intensity,technology input,and road network density.The results of the OLS regression model show that ecological environment has a negative correlation with population density,the average land value of second and third output,land use intensity,and road network density.The results also show a negative and then a positive correlation with technology input.